Analytical potential energy function characteristics

To effectively carry out studies of these types by means of an analytic potential energy function, the function must be constructed and parameterized so that it possesses certain crucial characteristics. These include the following ... 

Force fields describing intermolecular interactions can be in general classified into two categories (1) classical and (2) quantum models, the characteristics of which are outlined in O Fig. 21-1. Classical potentials consist of force fields that employ an analytic expression, in conjunction with several adjustable parameters, for the potential energy surface (PES) as a function of the coordinates of the atoms in the system. In contrast, for quantum models, the PES is computed by considering both the position of the nuclei and the distribution of the electrons of the system, and it is obtained by solving Schrodinger s equation. 

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